1. Field of the Invention
This invention relates to a method for implanting one or more porous devices, such as loops of small sized porous rope, cord or hollow tubes anterior to or under superficial layers of the cornea and limbal area with a portion of the loop of the porous material exiting on the ocular surface whereby ocular pressure is relieved by passage of aqueous humor through the device's porosity onto the eye's surface and thereby drained with the natural mechanism of tear fluid drainage. More specifically this invention relates to the method in which the pores in said porous material are small enough to prevent bacteria or other pathogen ingress.
2. State of the Prior Art
Glaucoma involves uncontrolled intraocular pressure within the eye caused by obstruction of aqueous outflow which may cause permanent damage to the optic nerve and retina. Surgical treatment of glaucoma has had limited success because of failure to control intraocular pressure as well as post-operative complications which may aggravate pre-operative increased intraocular pressure.
The eye is a complex organ. The cornea covers the front of the eye. Light is refracted by the cornea through the anterior chamber of the eye to the lens. The size of the entrance aperture of the eye, known as the pupil, is controlled by muscles. The lens is suspended by ciliary body zonules and focuses refracted light through the vitreous chamber onto the retina in the back of the eye. Ciliary muscles in the eye can vary the shape of the lens to focus on objects that are at various distances from the eye.
Aqueous humor is the fluid within the eye produced by the ciliary body, which fluid migrates through the pupil into the anterior chamber, through the trabecular meshwork and into veins which form aqueous fluid collection channels beneath the conjunctiva. When there is not sufficient aqueous humor outflow to relieve the intraocular pressure, glaucoma results.
Medical treatment of glaucoma has met with varying degrees of success. Eye drops, pills and laser photocoagulation are used to reduce the production of aqueous humor in the ciliary body and to increase the outflow of aqueous fluid through the trabecular meshwork.
Surgical procedures of various types have also been attempted to improve the outflow-facility. These surgical techniques are generally unsuccessful due to post-operative scarring of the wound site itself or the overlying tissue planes, which scarring prevents adequate outflow of the aqueous humor out of the eye and results in a recurrence of the uncontrolled intraocular pressure.
Several U.S. patents have shown implantation devices involving hollow needles or tubes which require valves or other means to prevent bacterial ingress or must be completely imbedded in the eye or under tissue planes to avoid any exposure of a duct which will permit bacterial ingress. Such patents include U.S. Pat. Nos. 3,159,161, 3,788,327, 4,402,681, 4,428,746 and 4,521,210. These devices are rigid and present possible discomfort as well as other problems.
A most recent operative treatment is the insertion of hydrogel setons in the space under the conjunctiva and/or contiguous tissue planes as described in U.S. Pat. No. 4,634,418 issued Jan. 6, 1987. However, this method, as described in col. 3, lines 45-47, states that the conjunctiva and/or contiguous tissue planes is closed over the entire surgical area to include the device. Therefore there is no provision for the aqueous humor to be exited directly unimpeded to the exterior of the eye. This distinction is important particularly since scarring of the conjunctival tissue and contiguous tissue planes can impede adequate egress of aqueous humor.